Heat-recoverable articles such as heat-shrinkable tubes are used as covering for joints between insulated electrical wires, wire terminals, metal pipes, and the like for the purpose of protection, insulation, waterproofing, corrosion protection, and the like. For example, when a joint between insulated electrical wires is covered with a heat-shrinkable tube and heating is performed, the heat-shrinkable tube shrinks, conforms to the shape of the joint, and adheres thereto, and thus the joint can be protected. In the heat-recoverable articles, it is required that heat shrinkage does not occur at ambient temperature before being heated, and that the heat shrinkage temperature is not excessively high so that there is no concern that an object to be protected may be adversely affected during heat shrinkage.
Examples of such heat-recoverable articles include a heat-recoverable article provided with a base material layer containing a polyolefin or the like. However, in the case where a copper material such as an electrical wire is covered with such a heat-recoverable article, the heat-recoverable article becomes degraded because of copper-induced damage in which copper promotes oxidation of the base material layer. Accordingly, in an existing technique, degradation of a heat-recoverable article is prevented by incorporating a copper inhibitor or an antioxidant into a base material layer of the heat-recoverable article.
Furthermore, in order to prevent copper-induced damage, a heat-recoverable article has been proposed which includes a base material layer obtained by incorporating a six-component stabilizer into a polyolefin (refer to Japanese Unexamined Patent Application Publication No. 6-176649).